Understanding video recording formats

How to tell your AVCHD from your MPEG

If you plan to shoot video with a camcorder or DSLR, you'll run across an alphabet soup of recording formats, with names like AVCHD and MP4. How do you know which one will work best for your needs? In this article, we'll go over the various ways in which video is processed and stored, as well as the types of memory available.

Hard drive and flash memory camcorders store videos as data files to a small built-in hard drive or microchip, similar to the way we store files on our computers or MP3 players. These kinds of camcorders come with varying amounts of memory, and their potentially enormous storage capacity is one reason for their increasing popularity. Plus, this kind of memory can be reused thousands of times without degrading.

A quick note on the difference: the advantage of flash memory is that it doesn't have any moving parts, so it's considered more durable than hard drive memory. It's less susceptible to recording errors if the camera is being moved quickly or jerkily. And camcorders with flash memory generally record and access media faster than hard drive camcorders. Given the tiny size of flash memory, these camcorders can be built smaller and lighter, too. Hard drive camcorders are currently available in greater capacities; however, they are becoming harder to find as flash memory's capacity has increased and cost has declined.

Camcorders that use videotape and DVD-based storage can still be found, but they are quickly giving way to the solid-state, file-based media revolution. You can safely assume that flash memory is most manufacturers' storage medium of choice.

Recording to memory cards

Memory cards, a type of removable flash memory, are especially handy when you want to add extra storage capacity to your camcorder. Almost every new camcorder on the market offers some form of memory card compatibility. When you run out of room, you don't have to pick which video segments you'll discard — you can just pop in a new memory card. The most common types of memory cards found in camcorders are SD cards and Memory Sticks®.

A camcorder with a memory card slot might also be a good choice if you're interested in sharing video clips online. These cams make it easy to record video clips and images to the memory card and then pop it into a memory card reader or card slot on your computer. Then you can upload clips to a video-sharing site, like Facebook® or YouTube™, or email them to friends and family. Memory cards are repeatedly re-useable, and with the cost-per-gigabyte of computer storage dropping, you can simply copy your video files to a big hard drive attached to your home computer once you've shot the card full. Then erase the card, and you're ready for re-use.

Safety note: As with your precious family photos or irreplaceable documents, it's a good idea to make another copy of the above-mentioned hard drive from time to time if you wish to have it properly archived. Even better, make a regular schedule for backup and then keep one of the drives in a different humidity and temperature-controlled location. You'll be covered in case one of your devices meets with harm. Cloud storage (the ability to back up your files to servers on the Internet), while a great thing for many kinds of files, is not a good choice for video due to video's large file sizes. The amount of data you'd have to transfer would be unmanageable.

File formats and codecs

The various formats and codecs sound confusing, but they group around a single concept: each is a different way to compress a large video file so it takes up less space when you store it. The most frequently used video codecs for camcorders and DSLRs is MPEG-4. It's a very efficient codec with fantastic image quality that delivers an impressive image-quality to file-size ratio. When you see H.264 and AVCHD listed in a camera's specs, those are sub-families of the MPEG-4 grouping. This codec can be used to compress files up to 4K resolution.

We should not ignore the effect of data rate. Regardless of codec, the total amount of data required per second to construct/reconstruct the video signal has an impact on picture quality. Higher data rate means higher picture quality. This means your memory device — hard disk or flash memory — has to be able to deliver the data rate the codec demands. For this reason, you're seeing faster classes of SD cards and faster hard drives with greater transfer speeds. Even computer video cards have limits on the data rates they can handle. It's important that you have the fastest storage devices you can reasonably afford for good video performance. The latest camcorders are offering significantly higher data rates for their top-quality capture profiles than were prevalent even a couple of years ago.